1. Field of the Invention
The present invention relates to an antiskid apparatus and more specifically to an antiskid control apparatus which is intended to improve stability under road surface conditions of split .mu. in which the coefficients of friction of the road surfaces, with which the left and right wheels make contact, differ greatly.
2. Prior Art
Previously, the apparatuses disclosed in Japanese Patent Application, 2nd publication, No. 56-28738, and Japanese Patent Application, 2nd publication, No. 59-19863, have been used as antiskid control apparatuses which prevent wheel lock during vehicle braking.
In the antiskid control apparatuses disclosed therein, the presence or absence of a tendency to lock in each wheel is determined based on the measured value of the wheel speed (which means the speed of the rotating wheel), and the locking of any wheel which has a tendency to lock is prevented by controlling the rise in the fluid pressure of the hydraulic system of said wheel.
As a result of the freezing of one portion of the road, etc., the coefficient of friction of the road surface with which the right wheel makes contact, and the coefficient of friction of the road surface with which the left wheel makes contact, may differ greatly. In such cases, countermeasures are taken against vehicular spin caused by an imbalance in braking force. That is, the rise in the brake fluid pressure of the wheel which is opposite to the wheel which is on the side which is antiskid-controlled (for example, the right front wheel which opposes the left front wheel, or the left rear wheel which opposes the right rear wheel) is controlled, and the sudden occurrence of the yawing moment, which is the cause of spin, is controlled. By means of this, a steering margin is provided to the driver, which ensures driving stability.
The above-mentioned spin countermeasures have been primarily developed for full-sized vehicles (in general, long wheelbases are best-suited to nonswerving forward motion during braking). Therefore, in recent years the problem remained that antiskid apparatuses could not be applied to compact vehicles.
In general, compact vehicles which have short wheelbases are inferior in nonswerving forward motion during braking when compared with full-sized vehicles with long wheelbases. In addition, the load on the rear wheels of compact vehicles, which has an important role in maintaining direct nonswerving forward motion, is low. As a result of this, in the above-mentioned conventional antiskid control, there are cases in which spin countermeasures achieved by lowering the speed at which the yawing moment occurs cannot alone ensure sufficient driving stability.